16 research outputs found
Effect of nonuniform hole-content distribution within the interlayer pair-tunneling mechanism of layered HTSC
The interlayer pair-tunneling (ILT) mechanism for high-
superconductivity is able to predict the dependence of the (optimal) critical
temperature Tc on the number of layers n within an homologous series of layered
cuprate oxides. We generalize the mean-field procedure employed to evaluate Tc
within an extended in-plane Hubbard model in presence of ILT, developed for a
bilayer complex (n = 2), to the case of n = 3, 4 inequivalent superconducting
layers. As a function of doping, we show how a nonuniform hole-content
distribution among different layers affects Tc. In particular, depending on
doping, the onset of superconductivity may be ruled by inner or outer layers.
The latter result may be related to recent experimental data of Tc as a
function of pressure in Tl- and Bi-based layered superconductors
Spin-phonon interaction and band effects in the high-T_C superconductor HgBa_2CuO_4
Band calculations show that a stripe-like anti-ferromagnetic spin wave is
enforced by a 'half-breathing' phonon distortion within the CuO plane of
HgBa_2CuO_4. This spin-phonon coupling is increased further by shear distortion
and by increased distance between Cu and apical oxygens. The effects from
spin-phonon coupling are consistent with many observations in high-T_C
materials. Spin-phonon coupling can be important for the mechanism of spin
fluctuations and superconductivity, although the effects are quantitatively
weak when using the local density potential.Comment: 4 pages, 1 figur
Review on Superconducting Materials
Short review of the topical comprehension of the superconductor materials
classes Cuprate High-Temperature Superconductors, other oxide superconductors,
Iron-based Superconductors, Heavy-Fermion Superconductors, Nitride
Superconductors, Organic and other Carbon-based Superconductors and Boride and
Borocarbide Superconductors, featuring their present theoretical understanding
and their aspects with respect to technical applications.Comment: A previous version of this article has been published in \" Applied
Superconductivity: Handbook on Devices and Applications \", Wiley-VCH ISBN:
978-3-527-41209-9. The new extended and updated version will be published in
\" Encyclopedia of Applied Physics \", Wiley-VC
Intrinsic and carrier density effects on the pressure dependence of Tc of high-temperature superconductors
The pressure dependence of
Internalization of staphylococcal leukotoxins that bind and divert the C5a receptor is required for intracellular Ca2+ mobilization by human neutrophils
A growing number of receptors, often associated with the innate immune response, are being identified as targets for bacterial toxins of the beta-stranded pore-forming family. These findings raise the new question of whether the receptors are activated or merely used as docking points facilitating the formation of a pore. To elucidate whether the Staphylococcus aureus Panton-Valentine leukocidin and the leukotoxin HlgC/HlgB act through the C5a receptor (C5aR) as agonists, antagonists or differ from the C5a complement-derived peptide, their activity is explored on C5aR-expressing cells. Both leukotoxins equally bound C5aR in neutrophils and in stable transfected U937 cells and initiated mobilization of intracellular Ca2+. HlgC/HlgB requires the presence of robust intracellular acidic Ca2+ stores in order to evoke a rise in free [Ca2+]i, while the LukS-PV/LukF-PV directly altered reticular Ca2+ stores. Intracellular target specificity is conferred by the F-subunit associated to the S-subunit binding the receptor. Furthermore, internalization of the two leukotoxin components (S- and F-subunits) associated to C5aR is required for the initiation of [Ca2+]i mobilization. Electrophysiological recordings on living cells demonstrated that LukS-PV/LukF-PV does not alter the membrane resistance of C5aR-expressing cells. The present observations suggest that part of the pore-forming process occurs in distinct intracellular compartments rather than at the plasma membrane